Brake mechanism



Jan. 18, 1938. E. STIFT BRAKE MECHANISM Filed Dec. 30, 1935 Patented 18,1938 UNITED STATES PATENT OFFICE BRAKE MECHANISM Edward Stift, St.Louis, Mo. Application December 30, 1935. Serial No. 56,618

claims. (c1, 18s-79.5)

This invention relates to brake mechanism for vehicles and moreparticularly brakes of the in` ternal expansion type. f ,y

An object of this invention is to providev brake mechanism simple inconstruction and efficient in operation. which will expand brake shoespositively in a radial direction to secure uniform contact with acooperating surface, or brake drum, throughout the entire surface'of thebrake shoes and which will be self-adjusting to auto-k matically providea certain minimumand a certain maximum clearance between the brake shoesand thecooperating surface.

Other and specific objects will be apparent from the following detaildescription taken in connection with the accompanying drawing.

Fig. 1 is a front elevation of brake mecha- -nism embodying myinvention; Fig. 2 is a vertical section approximately on l line 2 2,Fig. 1;

Fig. 3 is a rear elevation; and Fig. 4 is a vertical sectionapproximately on line 4 4, Fig. 2. A cam ring I is mounted for rotationon a lsupport 2 and has a plurality of cam surfaces 3 about itsperiphery. A plurality of brake shoes 4 are mounted about the peripheryof the ring and are adapted to be pressed outwardly by the can-i`surfaces 3 upon rotation of the ring. Springs 5 connected between thering I and the support 2 return the ring to and tend to hold it in avxed normal position. This normal position is automatically xed bymechanism comprising undercut teeth 8 on the inner surface of the ringand a spring pressed pawl 1 pivotally mounted on the support 2. The camring I is rotated by a ratchet mechanism comprising a Y pawl 8 and araton-9, the pawl being carried by a bell crank lever I 0 pivotallymounted on the 40 support 2.

The foregoing comprises a summary of the embodiment of the inventionspecifically illustrated in the accompanying drawing. The essentialfeatures of the invention are pointed out in the appendedl claims butthe following detail description will assist in understanding andpracticing the invention.

The support 2, as specically shown, comprises a plate which is lxed toan axle vor'axle housing. A front automobile axle is shown in the'drawing, the support 2 being attached thereto by screws II. 'I'hecamring I is mounted for rotation on the support 2 by having its innercircumference bearing on rollers I2 which are supported by studs I3secured to the support 2.

Inner washers Il and outer washers 'IB on the studs I3 engage the facesof the ring I and properly space and hold the ring against axialdisplacement. y

Each of the brake shoes has a pair of in- 5 wardly extending flanges I6.Pins I'I secured in the flanges I6 carry rollers I8, which ride theperiphery of the ca m disc I and which are engaged by a cam surface 3.In the specific embodiment shown four brake shoes are provided, Io eachhaving two rollers I8 and there being eight cam surfaces on the ring.

The brake shoes are held against circumferential movement by lugs I9,which are secured to or integral with the support 2 and extend l5inwardly to engage the edges oi the flanges I6.

The flanges I6 on the respective brake shoes A provide rigidity .for theshoes which are moved outwardly as a unit'in a radial direction by theaction of the cam ring I. The side edges of the 2o anges I6 are straightand are parallel to the radius of movement so that lugs I9 contactingthose edges serve as guides for the shoes, restraining the shoes frommovement in a circumferential direction and thereby prevent chatg;tering of the brake.,

Springs 20 connect adjacent ends of the brake shoes 4 and contract thebrake shoes when the cam disc is rotated to normal position.

In the operation of the device the bell crank ,an lever I0 is rotated bya rod 2|, which' may be connected to a foot pedal or lever not shown.The pawl 8 being engaged in 'a notch in the ratch 9 will rotate the camdisc I in a clockwisel direction (Figs. 1 and 4). The cam sur- :z5 faces3, bearing against the rollers I8, press the brake shoes outwardlyuniformly throughout their entire surface to contact a cooperatingsurface which may be the inner circumference of a brake drum, not shownbut well understood in 4o the art. If the clearance between the brakeshoes in their starting position and the brake drum is excessive due towear or ,for other reasons the ring I will be rotated by the ratchetsuch a distance that the pawl 1 will be urged by its spring 45 22 into asucceeding notch 6. Upon release of the rod 2|, the springs 5 willrotate the cam disc Il in a counter-clockwise direction with the springs20 contracting the brake shoes 4 while the rollers I8 ride the camsurfaces 3. The teeth 5G 6 being undercut provide a suilcient rotationof va cam disc I in a counter-clockwise direction so as to allow a xedminimum clearance between the brake shoes and the cooperating drum. Thisclearance will be in actual practice at least .01 56 inch. It will beseen lthat the function of the pawi I `and the undercut teeth l is toilx a normal position for the cam discA l so as to auto= maticallyadjust Lthe clearance between the brake shoes and its cooperating drum.

It `will be understood that various changesV may be made in the detailsoi' construction, withinl the scope of the appended claims, withoutdeparting from the spirit of this invention.

I claim:

l. In brake mechanism, a cam ring positioned and adapted when rotated toexpand brake shoes,

and means for automatically iixing a normal position of said ringincluding undercut teeth on the ring and a spring pressed pawlfor'engaging the teeth.

2. In brake mechanism, a cam ring positioned and adapted when rotated toexpand brake shoes, a ratch on the ring, a lever. a pawl carried by thelever engaging the ratch, and means for automatically xing a normalposition of thee'ringA position including undercut teeth on the ring anda spring pressed pawl carried by the support and engaging the teeth.

4. In brake mechanism, the combination comprisihg a support, a cam ringrotatively mounted on the support, a plurality of brake shoes about theperipheryof said ringand adapted to be pressed outwardly by rotation ofthe ring, yielding means for returning and holding the ring to and .in anormal position, yielding means for contracting the shoes. a ratch onvthe ring, a lever, a pawl'carried by the lever engaging the ratch, andmeans for automatically ilxing such. normal position including undercutteeth on the ring and a spring pressed pawl carried by the support andengaging the teeth.

5. In a brake mechanism the combination comprising a support, aplurality of rigid brake shoes. a pair of inwardly extending anges oneach or psaid shoes and spaced from each other, a pair of rollersJournalled between the flanges on each shoe, a ring mounted on thesupport and having a cam surface on its outer periphery arranged `andadapted to contact all of said rollers and thereby upon rotation topress the shoes outwardly in a radial direction by its rotation,straight edges at the ends of the flanges parallel to the radius ofmovement of the shoes, Iand means on the support contacting said edgesto restrain the shoes against circumferential movement.

EDWARD s'rrs'r.

